1. Field of the Invention
The present invention is directed to a liquid filtering vessel, and more particularly to a vessel for filtering liquids fed under pressure through a filter bag held within the vessel.
2. Description of the Prior Art
Liquid filtering vessels have been employed in industry for filtering various kinds of liquids through a filter bag retained in the vessels. Typical prior art vessels for use in carrying out the filtering operations by means of the filter bags are disclosed in the following U.S. Letters Patents.
1) U.S. Pat. No. 3,640,392 patented on Feb. 8, 1972 to Smith et al; PA1 2) U.S. Pat. No. 3,814,261 patented on Jun. 4, 1974 to Morgan, Jr.; and PA1 3) U.S. Pat. No 4,283,281 patented on Aug. 11, 1981 to Cogan.
U.S. Pat. No. 3,640,392 provides a filtering vessel comprising a top-open housing retaining therein a filter bag and a top cover connected to the housing by means of a hinge for swing-open and close the top opening of the housing. The top cover is formed with a center inlet for discharging liquid into the filter bag through the upper opening thereof. The center inlet is coupled to a pressurized liquid supply line through a liquid inlet passage formed in the hinge and through a liquid supply plumbing connection which is permanent and need not open be disturbed when the cover is open. In this patent, the liquid is directed down into the filter bag from the center inlet in the top cover in order to be uniformly fed into the bag and be filtered evenly through substantially the entire area of the bag for effective filtration at the expense of providing the liquid inlet passage in the hinge and a manifold additionally formed on the top cover for fluid communication between the inlet passage and the center inlet. However, because of that the liquid is fed under pressure from the inlet passage to the center inlet through the manifold or single channel in one fixed direction, the liquid will rush through the center inlet into the filter bag as being deviated or oriented toward the one circumferential portion of the bag. Thus, the vessel of this patent is still insufficient to provide a uniform liquid flow down into the filter bag, in addition to requiring a rather heavy structure of the top cover which is disadvantage for repeated replacement of the filter bag.
U.S. Pat. No. 3,814,261 provides a filtering vessel comprising a top-open housing retaining therein a filter bag and a top cover closing the top opening of the housing. The top cover is formed with an upwardly offset marginal portion which, in cooperation with an inlet port in the housing sidewall, defines a passage utilized to direct liquid from the inlet port upwardly and over the upper edge of the filter bag into the bag. In this patent, the liquid flow is limited to the one circumferential portion of the filter bag directly below the upwardly offset marginal portion of the top cover, resulting in a localized flow and therefore failing to supply the liquid uniformly into the filter bag which may leads in most cases to poor filtering efficiency.
U.S. Pat. No. 4,283,281 is directed to a like filtering vessel with a top cover fitted over the upper open end of a housing retaining a filter bag. A collar is provided around a housing sidewall to define a liquid flow path around the upper end portion of the housing below the top cover. The liquid flow path extends from an inlet port in the collar to substantially entire perimetric entrance to the housing upper end below the top cover, for directing the liquid from the inlet port, around the sidewall and over the upper end below the top cover, and into the filter bag over substantially the entire perimetric entrance thereof. This patent teaches to eliminate any liquid path in the top cover and instead to provide the circumferential liquid path around the upper end of the housing for directing the liquid into the filter bag over the perimeter of the housing.